Amazing result . Did myself a quick sim for about 7000 years in the past , and to my surprise the comet's orbit changes already between 50-100 years in the past , probably due to a close encounter with Jupiter . Really not stable .

Sorry for the slow reply. I didn't see your post until now. Usually I get an e-mail notification.

Running this comet backwards shows Jupiter gives it orbit-changing kicks in 2007 and 1958. Due to the chaos induced in the 2007 kick, I wouldn't trust that the 1958 kick actually happens. But it does show what is possible when a comet remains in a Jupiter-crossing orbit for a few decades. So Wiegert is probably correct. This comet is probably a relatively new-arrival from the Oort Cloud. Runing the simulation in either time direction will probably result in a kick back to the Oort Cloud, or a complete ejection.

You ran for 7000 years? You probably saw a lot of orbit changes. I'll have to let this run over night!

Yes , I ran a sim for 7000 years . I also created a close clone to the comet . Both orbits diverge very quicky , after some decades . The orbits become very chaotic. In the 7000 years I simulated I saw the comet wander out , sometimes wander in again , but in general wandering out, farther and farther , crossing Saturns orbit , then Neptunes orbit ... The result Wiegert announces doesn't surprise me .

To show what I got ....I've put the screenshots of the above sim in an animation. Sim runs 30.000 years back in time . Each screenshot covers 300 years . The animation shows the solar system from "above " , Pluto in white , Neptune in green, Jupiter in orange .

The yellow orbit represents the nominal path of the comet . The white orbit is a clone . Orbits are very chaotic and extend far beyond Pluto from time to time, but suprisingly the perihelia stay related to Jupiters orbit ( in this sim ).

Another simulation , covering 100 000 years to the past and involving 2 clones of 67P ( in white and red ; yellow being the nominal path) is animated hereby . All 3 orbits have the tendency to wander out to the outer solar system . One clone (the white one ) even gets a slingshot and is driven in an orbit of Sma 2000 AU and ecc 0.998 . So a birthplace far beyond Pluto may be a possibility. No of the 3 orbits however have perihelia far from Jupiters orbit after 100 000 y.